Since low-rank coal (low-quality coal) containing a large amount of water such as brown coal and subbituminous coal has a low heating value per unit weight, the low-rank coal is heated to be dried and pyrolized and is also upgraded in a low oxygen atmosphere to reduce surface activity. The low-rank coal is thereby turned into upgraded coal which has an improved heating value per unit weight while being prevented from spontaneously combusting.
For example, a rotary kiln-type coal pyrolizing device as follows is known as a coal pyrolizing device configured to pyrolize the dry coal produced by drying the low-rank coal. An inner tube (cylinder main body) is rotatably supported inside a fixedly-held outer tube (jacket). Heating gas is supplied to an inside of the outer tube (a space between the outer tube and the inner tube) and the dry coal is supplied into the inner tube from one end side thereof. The dry coal is then heated and pyrolized while being agitated and moved from the one end side to the other end side of the inner tube by rotating the inner tube. Then, the pyrolized coal and the pyrolysis gas are sent out from the other end side of the inner tube.